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What is the most economical way to store a small aircraft in a place with severe weather?
I'm interested in possibly owning a small aircraft sometime in the future.  In the interest of finding out how much money it would cost, I recently called a local FBO and asked about a hangar rental.  I was told that it starts out at over $300 per month and that there is an 18 month long waiting list to get one!  I am talking about an older used piston engine plane, not a private jet.
I'm quite aware of the fact that it is money, rather than aerodynamics that keep a plane in the air, and I'm getting the impression that it takes a lot of money to keep a plane on the ground, too.
The only other thing I know of is to tie it down, which I was told costs $150 per month at this same FBO.  The issue I have with that is concern about the weather.  I live at high elevation; the summer sun is very intense, thunderstorms and hail and common in the summertime and winter brings plenty of snow; sometimes up to two feet at a time.  Temperatures fluctuate from about 0 to 100 degrees Fahrenheit.
I was wondering if there are ways to effectively protect an aircraft from the elements while it is tied down, or if there may be some more cost-effective storage solution than a rented hangar.

Have you already gotten the license to fly that plane? Maybe your instructor can give some advice that suits your local condition.

No, this question is to help me make appropriate plans for when the time comes in the future.

Yes, planning in advance helps you getting prepared. I still suggest you to learn flying, see if you really like it before spending money. Also if you edit into the question the airport you plan to operate from will help make the question more specific.

@vasin1987 There's nothing in the question that even remotely suggests that Daniel is going to go out and buy a plane and rent hangar space before he's even learnt to fly.

take the wings off? It's less likely to wander off that way

You could join a group that operates an aircraft. For me it was the only financially viable way to keep current, and not spend all my money on rentals (A personal plane was out of the question due to cost in the UK)

For what it's worth, I pay $325/mo to park my car in a city parking garage, so $300/mo to park a plane seems pretty reasonable, especially when the airplane takes up 4 - 8 times more floor space than my car.. While land may be cheaper at an airport, hangars are not cheap to build or maintain.

@Johnny, I'm glad that I don't live wherever you live if it costs that much to park your car.

The air park just across the street from my work has "covered parking" with a steel/fiberglass awning over some tiedown spots; less than a full hangar enclosure, more than a basic tiedown (they have all three onsite). If you're worried about hail damage but can't afford or justify a full hangar, a covered tiedown is worth a look. Keep in mind this is good insurance for smaller hailstones, but this year my area has seen isolated pockets of softball-size hail that has punched through residential roofs, totaled cars in their garages, etc; a corrugated steel hangar won't fare much better.

Location matters.  Where are you located?  A hangar is not as important in a dry climate like Las Vegas as it is in, say, Miami.
It may make sense to pay more for a hangar.  Leaving a plane exposed to the elements you describe (0° - 100°, snow, wind, sun) will do damage over time.  The plane won't corrode into a heap but little things will start to require extra attention.  Those little things will add up at annual time.  It's unavoidable.  Having the hangar is another layer of protection that, in my opinion, is well worth the cost.  If a hangar is simply unworkable then think about a covered tie down. A covered tie down plus a decent cabin cover can accomplish about 75% of what a hangar offers at half the price.  You won't have complete protection from hail, vermin, or thieves but that's not a deal breaker.  Just lock the doors and keep the insurance up to date.
Are you considering a simple plane like a 150 (all metal, "affordable"), a tube and fabric plane, or something with more complexity like a Bonanza or Mooney?  Maybe a C-150 with rough paint, a worn interior, and old avionics that aren't worth stealing will do just fine outside.  If you buy something with good paint and interior (or fabric covering) you'll want to protect it.  New P&I costs thousands and thousands of dollars so it's much cheaper to keep a pretty plane pretty than to make an ugly plane pretty.  The costs to re-cover a plane in fabric can cost tens of thousands depending on the amount of fabric and complexity of the paint scheme.  Other airplane-specific considerations like corrosion on Mooney's steel structure (see Mooney Service Bulletin 208) or a Bonanza's magnesium control surfaces should be factors in your decision as well.  Finally, when you go to sell the plane a buyer will likely feel much better about a plane that was hangared than one that was parked outside.
One piece of (unsolicited) advice: draw up a conservative budget assuming that costs will be higher than expected.  Budget for a hangar, $1M smooth insurance, and a tough annual during the first year of ownership.  Multiply this number by 1.5 at the very least.  This is a "bad case" first-year cost (don't worry, it gets better as you settle into ownership).  If you can absorb that cost without feeling any pain then you're ready for ownership.  If you can't...who cares?  Buy the plane anyway!
We can give you a more complete answer if you know the answers to the following questions:

where are you based?
what kinds of planes are you looking at?
what is the current condition of this hypothetical plane?
what's your maximum annual ownership budget?

In the interest of following the site guidelines and not making the question about myself personally, I omitted my exact location, but since you have asked, I live near Denver.  The FBO I called is at the "Front Range Airport", a few miles east of Denver International Airport.  And just so I said it, I hope that you kidding when you say "Buy it anyway!"

Owning a plane is a lot like owning a boat or any other expensive "toy" that doesn't come without some pain of ownership. Personally I own a 1/9th share in a Cardinal 177, my dues are cheap, the aircraft is cheap, and the hanger is paid for. I'd look into flying clubs before jumping into ownership... @DanielAllenLangdon

I know front range.  I flew cargo from DIA for a few years.  I'm half joking when I say buy it anyway.  If you think you can make it work, go for it.  You can worry yourself over imaginary scenarios forever but you can only fly your own plane if you buy one.  Regarding parking, Front Range open air parking isn't the end of the world but consider Centennial's covered parking option if it's not that much further away from you.  An extra 10min drive would be worth having some protection against the elements.  Also think about equipping with an engine pre-heater.

Ah, you mention "covered parking".  Is that some sort of option between open air parking and parking in a hangar?

Yes.  It's an airplane version of a carport.  Google "shade hangar" to see examples.

Cool!  That may be the ticket because from my experience with the weather here, I'm rather concerned about sun and hail.  I hate to imagine spending big $ only to find my beautiful new toy covered in dimple marks from marble-sized chunks of ice falling from the sky.  If you haven't, sometimes you should hear the sound it makes when that hail comes down on your car :-/

The way to answer this is to determine whether the convenience and lower maintenance of hangaring your airplane is worth the financial cost of it. \$150 per month is \$1800 per year, would 10 years of being outside cost \$18,000 in damage you'd need to fix? Is having a nice, warm and dry airplane when you want to fly worth the extra cash? It's also much more secure in a hangar, if you have nice expensive instruments and equipment a hangar will help protect them from theft.
High altitudes with lots of snow are hard on airplanes. The high UV wears paintwork fast, damages acrylic windows, and reduces the life of fabric coverings. Extreme cold and snow, plus exposure to moisture will damage wood and fabric much more than metal, but it's still more wear on an all-metal airplane.
Still, \$18000 is a lot of money, and on a metal airplane you could mitigate a lot of outdoor damage with a good cover. I don't see it being financially worth it to hangar an all-metal airplane. Fabric airplanes are expensive to re-cover and replace wood on, so it is probably worth it for one of those. As for the convenience and security factor that's something you will need to determine for yourself.

Look into whether or not it is possible to rent space in someone else's hangar.
That's what I do.  My landlord keeps his own plane in the hangar, but there's enough room for mine as well.
I have personally seen a Decathlon and 2 single seat Pitts in a single standard T-hangar.
Be creative!

I managed 5 Cessna for a flying club in Texas; where weather could be severe and summer heat intense. We kept the planes outdoors and in 5 years only suffered one incident of hail damage, even survived a passing hurricane.  Planes are tough.
One disadvantage to hangering a plane is getting it in/out.  If you fly often then waiting to have your aircraft shuffled in/out takes a while each time. But 300 dollars per month is not just the going rate, it's on the cheap side for a hangar.
I agree that a covered (carport) option is close to ideal = fast in/out yet protection from hail and beating sun.  If you are flying larger stuff, then obviously money is not a hindrance and a hangar is ideal.  But if 300 per month is unattractive, you are obviously new to aviation and will soon not think it's so much.  And when you end up divorced because of your airplane, welcome to the club!

When you say that you only had one incident of hail damage, is that because you only had one hail storm, or because your equipment holds up in spite of hail?

"But if 300 per month is unattractive, you are obviously new to aviation and will soon not think it's so much."  Couldn't agree more.  There is a tounge in cheek way to refer to money spent on airplanes: Aviation Money Units, or AMUs.  1AMU = $1,000.

acpilot, you remind me of what I heard about boat ownership on the radio years ago.  If you think that a boat is something that floats on water, you are mistaken.  Boat is an acronym; the letters stand for Break Out Another Thousand.  But seriously, regardless of how much something costs, one doesn't want to unnecessarily pay too much for something.

300 dollars per month is not too bad. Up here in the northeast, west of Boston, it's 500 per month.  I'll be tied down outside for just 125.

you could try a low cost tie down ~$50/month in Northern California for small aircraft storage and use a cover, here is a little more info and pictures of the site

authors: владимир корольков


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Can I simply use multiple turbojet engines to fly supersonic?
the jet engine FJ33 produced by Williams International produces around 6 kN thrust (maximum, at sea level).
Imagine: to fly supersonic, I need for my aircraft 9 kN of continious thrust.
I am wondering now: is it possible to use just two FJ33 jet engines, so that I would just double the maximum thrust ?
What are the restrictions to this?
My thoughts:
If I fly supersonic with a jet engine which is designed actually for subsonic flight, there can be many aerodynamic effects like stall and strong rise in drag at the gondola, for which the engine is not designed: So I would need a diffusor to bring the supersonic flow down to an optimal flow velocity for the FJ33.
Is this correct? Do you know some other restrictions?

When you calculated 9 kN of thrust required, that calculation worked from some assumed aircraft weight and size... more thrust required to push the Concorde supersonic than for an F-16. Adding another engine changes the weight & size & shape of the aircraft. So the new aircraft will probably need more than 9 kN to go supersonic. Add enough motors (with proper inlet/exhaust geometry & etc) and you'll have enough thrust, but the resulting tradeoffs (range, payload, etc) may make the final design pretty different than what you started with.

There may be just a few restrictions related to your chosen airframe.  (Which you neglected to mention)  And you will probably need an STC, depending on your country.
Anyway, you might be able to get supersonic, pointing downhill, at least once...

Not seeing the cause for downvotes. As an entry-level, conceptual question, this seems to be reasonable. "What's so hard about going supersonic, just add more engines, right?"  Clearly it's not that simple, but let's explain why not.

@Ralph J, good point, but I downvoted it because it doesn't read like a well thought out conceptual design question.  It reads like "I want to bolt an extra jet engine on MY AIRCRAFT to see if I can fly supersonic."  (The image that comes to mind is the infamous Darwin award winner who strapped a JATO bottle to his car...)

@MichaelHall Yeah, that Impala went supersonic, briefly... once.  Even if it's utterly apocryphal, that's just a great story.

"gondola"? Are you trying to make a supersonic hot air balloon?

@pericynthion Why not? Happens in FSX: Steam Edition all the time. - lol

Personally, I would be more concerned with "Will my airframe disintegrate if it reaches supersonic speeds?" than "Will strapping an extra engine onto my airframe allow it to achieve supersonic speeds?" You might be able to achieve supersonic speeds even without an extra engine, simply by entering a steep dive in a clean configuration with max thrust selected. But your airframe also might disintegrate if it isn't designed for supersonic flight.

Yep, as long as you bolt on 50 to 100 nominally-sized turbojet engines, you are sure to be able to fly supersonically.

@MichaelHall -- re "And you will probably need an STC"-- the question appears to about the engineering feasibility of said concept, which is arguably unrelated to any regulatory requirements--

How fast do you want to fly? Breaking the sound barrier adds lots of complications, and there's not much benefit if you're only going to fly at Mach 1.1 anyway. Concorde could fly at Mach 2.

Ever drive Parley's Summit (I-80 east of Salt Lake) in a '78 Impala?  You'll need a JATO bottle if you want to keep up with traffic...

is it possible to use just two FJ33 jet engines, so that I would just double the maximum thrust ?

Yes, you will double the maximum thrust on the ground and at rest. You will also double thrust at altitude and flight speed, but that thrust will be much lower than your sea level static thrust. Below is a thrust diagram over speed and for several altitudes for a small turbofan engine with a bypass ratio of 3. It is not the Williams, for which I don't have this kind of diagram, but very similar.

The kink in the low level thrust line is from internal engine pressure limits. At low altitude and high speed the pressure inside the compressor and burners must be limited so they will not be overstressed.
Below 10,000 ft it is not legal to fly faster than 250 kts and supersonic flight is illegal over a lot of areas. In order to achieve legal supersonic flight you need to be high and over unpopulated land. The higher the better, but as you can see from the diagram, thrust drops with altitude. For turbofans it also drops with airspeed. Now it would be interesting to know at what altitude and speed those 9 kN of thrust are required - maybe that number is for a lower altitude and the two FJ33 are indeed sufficient. At the moment that question is unanswerable with the information given.

So I would need a diffusor to bring the supersonic flow down to an optimal flow velocity for the FJ33.

Yes, but that is simpler than it seems. Every engine intake will slow down and pre-compress the incoming air stream at high subsonic flight speed simply because the engine will not be able to swallow all the air that could flow through the intake at high speed. Instead, some air will spill over the intake lips so only the core of the streamtube that flows toward the intake will be ingested. At supersonic speed the intake will do this precompression by means of a shock, the strength of which is again influenced by the swallowing capacity of the engine. Still, the intake cross section needs to widen between the intake face and the engine face and must be carefully shaped to avoid flow separation or speed variations at the engine face (that is actually the tricky part) or you will not be able to achieve the full performance of the engine. A simple pitot intake should be sufficient but it will need some length to do its work properly. Therefore, it is advisable to not put the engine in gondolas (B-58 style, also called nacelles) but to integrate them into the fuselage.
Thrust is the difference between intake an exit impulse, so you need high exit speed in order to have useable thrust at supersonic speed. While a simple convergent nozzle can be used to achieve supersonic flight, the best results are obtained with a convergent-divergent nozzle. Due to the high temperature of the exit flow, even a subsonic exhaust stream will bring you to supersonic speed, but only just. Given the relatively high bypass ratio of the FJ33, if supersonic flight is achieved, the maximum Mach number in level flight will not be much above 1 (if the drag characteristics of the airframe allow even this).

Great answer Mr Kämpf, thank you, helps me a lot !

Digression - It is not illegal to fly fast and low, it just requires permission. Large commercial aircraft would normally climb at V2+100 and at load, that can easily exceed 250Kts. The controllers know this and don't hesitate to grant permission.

@PaulSmith The linked answer says the same, but I selected a very brief and necessarily imprecise term.

There are actually two questions in this post, which I'll address separately.
The first question is "Does the thrust from multiple engines add together?" And the answer to that is yes, so long as both engines are mounted so that their thrust vectors are parallel, two engines, each producing 6 kN of thrust, will produce a total of 12 kN.
The second question is "Can I just bolt a second engine onto my airplane to make it go supersonic?" There's not enough information here to accurately answer that question, so the closest I can get is "probably not".
The maximum thrust of the engine doesn't matter. What matters is the actual amount of thrust produced by the engine in the conditions you expect. You mention the maximum thrust is achieved at sea level. But you're not likely to be flying at sea level, are you? You're going to be flying much higher, where the air is thinner and therefore wind resistance is much less, but you're not going to get the full 6 kN at those altitudes. An engine designed for subsonic speeds also isn't going to produce its maximum rated thrust at transonic or higher speeds, so you're also going to lose thrust as your speed increases.
There are other factors too. There are all sorts of interesting shock waves that form in the transonic region, which could either starve your engines of air, force too much air into them, or even damage the turbines. Adding baffles as you mention is going to add a lot of drag, which will need more thrust to counter. Another consideration is that the simple weight of the engine will require more thrust to lift. So even if your "9 kN" calculation is accurate for the plane as-is, it's not going to be accurate after you've made all these modifications to it.
Another thing to consider is the strength of the airframe. If you put a second engine on a frame not designed for it, you're going to damage and probably destroy it.

Thank you hiddenWindshield!

In general, the answer is no. The two classes have different characteristic exhaust velocities. However, some subsonic engines can be persuaded to attain modest supersonic speeds.
A subsonic turbofan, such as the Williams FJ33, is designed for maximum efficiency at subsonic speeds. It therefore has a high bypass ratio, meaning that the fan greatly increases the mass flow of the engine, while limiting the overall exhaust velocity. This maximises the thermodynamic efficiency of the engine, and hence also its fuel efficiency. The exhaust nozzle is shaped to allow air out without building up a back pressure which would reduce mass flow. Typically it is of convergent profile, which accelerates the exhaust backwards and thus converts some of the exhaust temperature and pressure into thrust.
A supersonic engine has to accelerate the exhaust much harder. To obtain a given thrust, it therefore needs less mass flow and so its bypass ratio is much lower (a pure jet has zero bypass ratio). But supersonic airflow within an engine, especially its "hot" end, is undesirable. So, to maintain high exhaust speed the temperature of the exhaust is raised, also raising the speed of sound in it. The exhaust thus "thinks" it is still subsonic. The exhaust nozzle is shaped to maintain the back pressure needed to maintain that temperature, but still somehow provide additional thrust. It is typically of convergent-divergent profile; the convergent section helps to retain the back pressure, while the high-pressure exhaust passing from there into the divergent section then expands rapidly sideways, its pressure thrusting against the angled sidewall to create significant thrust.
So you can see that merely adding a supersonic intake duct is nowhere near enough; subsonic turbofans such as the FJ33 are just not cut out for the supersonic role, their low exhaust velocity prevents anything more than the most modest supersonic speeds. You might in theory add an afterburner (reheat) and reshape the exhaust nozzle, but that would massively increase fuel consumption. The performance and reliability of the engine core would also suffer, as it would not be optimised for such a pressure and temperature regimen.

Great answers, thank you, helps me a lot !

Another important thing to bear in mind is that aerodynamics work quite differently at supersonic speeds.  While you can make anything go fast if you push hard enough, an aircraft that’s not designed for supersonic operation would likely be uncontrollable under those conditions.

That is well worth to be considered. For the nitpickers: This is a valid answer, because it addresses the "simply" in the question. No, supersonic flight is not made possible by just simply adding more thrust.

@PeterKämpf "No, supersonic flight is not made possible by just simply adding more thrust." Well, not just by adding more thrust, using air-breathing engines. If you're using rockets, "more thrust" is likely to suffice.

@nick012000 Momentarily maybe, but not in a sustained way if you cannot trim the changed lift distribution at supersonic speed. Add to that new forms of flutter and aeroelasticity and sustained supersonic flight turns out to be non-trivial.

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What is this three-engine beauty?
What is this three-engine beauty?

It appears to be a Westland IV/Wessex
I don't know why it is marked P-1, but the elevator is distinctive.

P-1 is a temporary civilian registration issued to the company to use on prototypes. Each company was assigned a letter, so any time you see a British civilian aircraft with a letter-number code like this, it is a prototype. The best known are probably E.2 to E.3 used for the de Havilland Albatross airliners, as seen below:

Hi Mike, the question asked it was about the type of airplane in the photograph, not so much the number on the side. That’s an interesting addendum though.

well, the sole answer was unsure of the importance of the number, and my answer added that it was a prototype Wessex, not just any Wessex.

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What effect does the Space Shuttle have on the Shuttle Carrier 747
I saw a picture of this the other day and it got me thinking... How does having the shuttle on the back of the 747 affect the factors of flight? My guess is that is provides an incredible amount of additional drag and obviously weight. What I'm really wondering is do the wings of the shuttle provide some sort of additional lift to the entire aircraft?

related: https://aviation.stackexchange.com/q/60708/1467 https://aviation.stackexchange.com/q/59807/1467 https://aviation.stackexchange.com/q/23801/1467 https://aviation.stackexchange.com/q/22022/1467

Excellent podcast with interview with a pilot that flew it.

Short answer-- "none any more", sadly

Your exact question has been answered before, so I recommend looking at all the links Frederico has listed. The questions/answers will also appear in the 'Linked' section on the right.

thanks guys, giving the podcast a listen

I bet the angle of momentum is drastically changed, I mean, it would clearly be drastically changed!  It must feel hugely different in roll.  I bet you'd have to be incredibly delicate about small rolls!

@fooot beat me to it in the comments but the linked podcast answers all your questions
The shuttle effected lots of factors of flight, in quick summary (from the info in the podcast) the whole assembly was:

...aerodynamics not neutral as is answered in this question
...Speed limited due to the braces that held the shuttle on
...VFR only due to the fact that impacting rain could cause water build up issues in the heat shield tiles
...Altitude limited
...Bank angle limited
...Quite short range by default
...Required the orbiter to be empty (although hypergolic fuels were left onboard. All payloads had to be removed if the orbiter was returning something.
...Required rib re-enforcements where the braces were mounted
...Was quite noisy due to the brackets used to hold the orbiter on

very interesting, will definitely give that podcast a listen, thank you

They shuttle carrier aircraft is modified as per the requirements of NASA. For instance, the fuselage is strengthened, vertical stabilisers are added and struts mounted. However your question pertains to the impact on the shuttle carrier performance, which includes (from Wikipedia):

Flying with the additional drag and weight of the Orbiter imposed
  significant fuel and altitude penalties. The range was reduced to
  1,000 nautical miles (1,200 mi; 1,900 km), compared to an unladen
  range of 5,500 nautical miles (6,300 mi; 10,200 km), requiring an SCA
  (shuttle carrier aircraft) to stop several times to refuel on a
  transcontinental flight.[4] Without the Orbiter, the SCA needed to
  carry ballast to balance out its center of gravity.[3] The SCA had an
  altitude ceiling of 15,000 feet (4,600 m) and a maximum cruise speed
  of Mach 0.6 with the orbiter attached.


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Why do gliders need more rudder when flying straight?
I came across a Captain Joe video in which he had said that gliders require much more rudder in straight and level flight, as opposed to powered aircraft. Can someone explain the reasoning and physics behind this?

The other thing that is so different to flying a propeller-driven plane is, you really have to use the rudder a lot to fly straight and level. You don't do this much actually in a propeller-driven plane or on the jumbo, I mean only for the landing, really, or for takeoff. But other than that, you don't really use the rudder much.
So, here, I'm constantly in the rudder pedals, trying to keep this little bit of wool [ed.: video panning to the sideslip indicator] actually nice and straight, there we go!

It's more hands-on and I think here you really learn to fly. We realized just today that I didn't use as much rudder as Stefan did, so that just goes to show that in a propeller-driven plane you don't use the rudder as much, only maybe in a turn, and for landing. And obviously in the jumbo, you don't use it at all, just also for takeoff and landing.

I've learned a lot today, especially in terms of, like, you know, using the rudder again and finding thermals.

The only reason to constantly hold some rudder input in actual straight-and-level flight is to compensate for thrust asymmetry effects like P-factor, rotating slipstream, etc.  So, if you were understanding the caption correctly, it was wrong.
On the other hand, if you are making aileron inputs to bring the aircraft back to wings-level after slight disturbance, you'll find that in order to keep the ball or yaw string centered, you need to make much greater rudder inputs along with those aileron inputs in a glider than in an aircraft with a lower-aspect-ratio wing, due to greater "adverse yaw".  So to keep the  aircraft close to wings-level in air with any amount of turbulence, yes you'll be moving your feet around a lot more in a glider than in an aircraft with a lower-aspect-ratio wing.
(PS -- by "level" in a glider we really mean "nearly" level.  In aviation, "straight-and-level" refers to the trajectory of the flight path (i.e. constant altitude), not the pitch attitude of the aircraft.  Normally gliders are always slowly descending, unless flying in "lift", i.e. rising air.  No one spends any time trying to hold an actual constant altitude in a glider.  But a slow glide at minimum sink rate speed or best glide angle speed is a close approximation of that.)

That’s what I thought, It seemed a little confusing when I first heard it.

I edited the relevant quotes into the question. The OP probably should have done this from the get-go.

I saw this same video and had a similar question. I thought he was talking about keeping the plane straight on the yaw axis when he was being towed.

Modern sail planes like the one he was flying are built with less yaw stability
because it is more efficient to have smaller stabilizers.

I dunno, a glider like a Grob-103's vertical fin isn't that much smaller than say a Cessna 152's, is it?  And it's acting at a longer moment arm, plus the destabilizing side area of the fuselage ahead of the CG is a lot smaller on the Grob than the Cessna.  (On the other hand, the Grob doesn't have a whole bunch of fuselage side area way aft of the CG either -- that actually might be most importance difference between the two in terms of yaw dynamics, other than span and aspect ratio.) I still think span and aspect ratio are ultimately the dominant factors in creating the difference.

One more comment, many older gliders had even smaller fixed vertical stabilizers (but larger rudders) than modern ones.  (E.g. Schleicher Ka-6 and Ka-2 / Ka-8, and especially Scheibe Bergfalke.)  The resulting effects in terms of yaw stability dynamics, especially if the pilot decided for some reason to take his feet off the rudder pedals entirely were-- as you would expect.


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How to get from IAS in MPH to KCAS using POH graph of best TAS/GPH?
My understanding is that in order to find the V(L/D)max I can do the following steps:

Look in the Pilot's Operating Handbook (POH) and find the performance reflecting the best TAS/fuel flow.
Find the KTAS for the determination from step 1.
Use a flight computer to get the KCAS from step 2.
The number from step 3 is V(L/D)max.
V(L/D)max / 1.316 = Vbe
V(L/D)max * 1.316 = V-Carson

While this sounds logical, I do not see any clear path from step 1 to step 2.
I looked up the definition of TAS, and it is related to EAS.  But when I look up EAS, it is dependent on TAS.  So when you do the algebra, it simplifies down to TAS = TAS and EAS = EAS, which is nonsensical, circular, and unhelpful.  Maybe I am not looking at the right equations, I’m not sure.
Do most pilots have flight computers with which they can determine KCAS starting with the value described in step 1?  If not, how should this best be done?  I could estimate air pressure using altitude, though it would not be very accurate, but I feel like there must be a better way given the large amount of instruments and tools available to most pilots in the cockpit.

If you're looking for best glide speed V(L/D max), isn't that an aerodynamic speed, and as such is based on CAS, not TAS?  Most aerodynamic speeds happen at the same CAS at different altitudes and temperatures, and so should use IAS instead of TAS.  Second, I'm curious about why you want to use MPH.  Usually since cockpit instruments are in knots, mph is only used for ground speed.  (Ground speed is TAS with wind speed and direction taken into account).

Someone told me that a lot of recreational pilots use mph, I don't know if it's true. I use kts. Glide speed is not the same as V(L/D)max because glide speed does not account for having a working engine (it's calculated for when your engine busts, thus why you find it in the emergency procedures section).

Several questions here that need answers;
V(L/D max) is best glide speed.  Look it up under emergency procedures in the POH.
Airspeeds:
TAS is EAS corrected for temperature.
EAS is CAS corrected for compressibility.
CAS is IAS corrected for installation errors.
IAS/CAS correction is available from the POH.
Pilots can use an E6-B flight computer to convert between CAS, EAS, and TAS.
For more on this topic; here's a good link

I am in communication over email with Mr Erb currently, and have read his article and Carson's. I think et glide speed is only an approximation of V(L/D)max because t does not take into account the difference in wetted area and power you get from a working motor and prop. Glide speed in the emergency section of the POH is for when your engine fails.

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To what extent is the clerical work (i.e. amending flight plans, logging, etc.) of a center air traffic controller now automated?
Specifically, do center controllers have to manually amend every flight plan now that En-Route Automation Modernization (ERAM) is fully implemented in the USA? To what extent is the process automated?
I know that, once the flight is en route, if the computer predicts a conflict the controller will need to okay a flight amendment. When flight plan requests are sent in and the center computer checks their viability, do controllers still have to give the okay to amend them and send them back?
Essentially, my question is this: what do FAA center air traffic controllers currently (I say currently because of when ERAM was implemented) do besides talking to the pilot?

What is ERAM? Which part of the world are you addressing in your question?

ERAM stands for En-Route Automation Modernization. It is part of the FAA's Next Gen program, and recently replaced the Host computer as the backbone of Air Traffic control centers (ARTCCs). It was fully implemented (at all 22 air traffic control centers in the US) early in 2015, and among other things automated a number of the air traffic control processes. I was addressing those 22 centers in general.

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Would there be any benefit in placing the aircraft engines on the elevator (end-tips)?
Looking at the HondaJet, we can see an interesting placement of the engines.
This leads me to wonder, for a slow flying aircraft how would it be affected with engines placed on the end tips of the elevator? (In other words, at the very edge of the left and right elevator wings.)

Related question about the CL-400, which was a fast plane concept using this placement.

There are some issues with placing engines in the horizontal stabilizer tips (I'm assuming you mean putting the engines in stabilizer- elevators are the control surfaces):

The engines are heavy- putting them at the rear shifts the c.g aft. The associated change in the c.g requires a larger horizontal stabilizer.
Putting the engines in horizontal stabilizer tips mean that it has to be strengthened, increasing the weight
Also, the fuel lines etc. has to be routed through the elevator, which increases complexity and weight penalty (not to forget the control surfaces which have to be there, which places a lower limit on the horizontal stabilizer size).
Not only the engine weight has to considered, but also the fact that the thrust has to be transferred from the engine, which furthers the weight penalty.
Noise in the rear of the aircraft- though this can be reduced by placing them away from fuselage, this further increases the weight.
Another thing to consider is that the engine may be affected by the wing wake, especially at high angle of attack.


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What are the consequences of disobeying cabin crew during emergency?
I was wondering what would be the consequences of disobeying flight crew due to emergency.
I was watching a video of Singapore B773 enroute on Jun 27th 2016 that landed, had a wing on fire, and passengers were made to sit and wait with the plane on fire. I would find it very hard not to attempt to evacuate plane.

Similarly people who try to retrieve their carry on luggage

The worst possible consequence of disobeying the flight crew is death. Yours, or you cause someone else's, or both. One example: In a water landing, all too many people inflate their life jackets before evacuating the plane. This is almost a guaranteed death sentence.

@MichaelHampton: Following your reasoning, if someone is going to cause my death, then wouldn't it be better to rush off the cabin before that happens, including against crew orders that can't prevent fools to inflate their life vest?

@mins And get sucked into a burning engine? No thanks. The time for running for the exits is when it's called out, or when the plane is in pieces.

I don't think there is an answwer to this question. Consequences could be death of everybody on board or survival of everybody on board. It kind of depends on the situation and what you are doing.

This question really needs more clarity since there are thousands of possible scenarios, even similar to the case you describe.  By "disobeying cabin crew" do you mean evacuating when told to remain seated? Is everyone disobeying or just one person?  Are you talking about legal consequences or physical consequences?  Is the imagined evacuation successful or unsuccessful? (in reality you probably wouldn't get far)  Is it a situation with real and manifest danger to the passengers or are the passengers just overreacting?

There are laws which mean you must comply with crew orders at any time whilst on an aircraft. This is especially important in an emergency. In the Singapore example, imagine if a passenger had, without thinking (as tends to happen in emergencies), opened up a door on the side that was on fire. Fire could have entered the cabin, ensuring fatalities.
However, no prosecutor is going to pursue charges against someone for disobeying directions in an emergency, unless their actions clearly led to serious harm. Every evacuation, so many people stop and try to get their carry-on items, when they are clearly told not to. Even though this increases the chances of other people dying, nobody has been prosecuted for that (to the best of my knowledge).

I'm curious about the laws applying to a stubborn Swedish citizen opening in Dakar, against crew orders, the door of a Lufthansa aircraft departed from Rio for Berlin, but forced to land in Senegal due to a fuel leak. And where would the criminal trial occur? (not asking for civil court).

Not a lawyer, but there are a few possibilities here. Since such an event would, in all likelihood, entail an emergency landing, the local authorities would be in the best position to immediately press criminal charges against the individual in question. Failing that, Germany would certainly be able to press charges, as the individual endangered a German aircraft, crew, and multiple German nationals. Lastly, any non-German or -Senegalese government whose nationals were present on the plane might also be able to press charges against the individual, since he put their citizens in danger.

@mins What happens in that scenario is defined somewhere. I think in that case Senegal and Germany would both have jurisdiction - but that sounds like a good question to ask and get a complete answer!

@mins the law of the country you are in are the only ones that automatically apply. The laws of your own country may also apply to your abroad. In that case, you'd be in Senegal so Senegalese law would apply.

@JonStory: Actually, any law that says it applies, does apply. For example, Belgium has an article in its criminal code for Crimes Against Humanity, and this article explicitly states that always applies, no matter the place, the nationality of the victim, the perpetrator, or the person filing the complaint. There doesn't have to be any relation to Belgium at all, Belgian courts will try any and all cases of Crimes Against Humanity brought before it. The question is, of course, does the accused care? Unless he plans to spend a holiday in Belgium, probably not.

E.g., some notable individuals that have nothing to do with Belgium, that have had complaints filed against them for crimes which had nothing to do with Belgium against people that had nothing to do with Belgium by people who have nothing to do with Belgium, include George W. Bush, Donald Rumsfeld, Dick Cheney, and Lynndie England. However, AFAIK, prosecutors refused to prosecute in all of these cases, so none of them ever went to court (let alone a verdict). I'm mentioning this only as an example of an instance, where a law is applicable for no other reason that the law says so.

I'm assuming that due to the highly-regulated nature of international air travel, there are probably treaties between ICAO members that define applicability of laws in precisely such difficult questions.

@JörgWMittag true, but that's a very strange, niche Belgian law, and would only be applicable if you subsequently travelled to Belgium.

@JörgWMittag: Thanks for the details, there is indeed something similar in France that states when French jurisdictions are competent. But I was wondering about other regulations, likely unknown to the pax when boarding, and possibly with a disproportionate harshness according to the pax own country laws.

The consequence would be to decrease your chance of survival. It's all about controlling chaos. Evacuation in an orderly controlled fashion increases the chances of survival over a chaotic rush for the door.
You are only interested in yourself, but the training that the crew goes through is to increase the survival of the highest number of passengers. Sure, your mad rush for the door may save yourself and possibly a couple others behind you but the stampede behind you is not as efficient of evacuation as an orderly controlled evacuation.
History has taught that the chance of chaos is increased if passengers get up from their seats before the plane comes to a complete stop. So the crew puts on their best authoritative voice and tries to make you sit there until the odds are optimum.
Your best chance of survival is to do exactly what the crew says to do. Their training is based on lessons learned from previous real life accidents.


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How did the Thrust Reverser Deploy in Lauda Air Flight 004 crash?
How did the electronically controlled thrust reverser in Lauda Air Flight 004 (which crashed) get deployed in mid air without the pilot command. Was there a fault in the electronic controller, a hardware or software fault?
In his book Air Disaster Volume 2, the aviation writer Macarthur Job wrote

had that Boeing 767 been of an earlier version of the type, fitted with engines that were mechanically rather than electronically controlled, then that accident could not have happened.

How could that incident not have happened in a mechanically controlled engine?

There are several questions in your post, you might either refine your intended question. Are you more interested in the root cause or whether a mechanically controlled thrust reverser could suffer the same failure?

also, a related question: http://aviation.stackexchange.com/questions/13259/why-are-thrust-reversers-so-unreliable

The FAA and official investigators could not determine the cause for the thrust reverser deployment. The FDR was completely destroyed. There isn't any way to tell why, hardware or software, that the thrust reverser deployed on 004. There is no factual answer to the first part of this question unfortunately.

Like Ron said, they were never able to determine the exact cause. In addition to the damaged FDR the actual components were looted from the crash site and when they got then back they had been tampered with. The airline was apparently none too cooperative in providing the maintenance records and what was provided was missing sections. Through testing they identified a few different failure modes but with no way of determining if they had occurred. I'd say that writer you quoted is going on specious assumptions

If the FDR was destroyed and no evidence was found to support the theory of a thrust reverser deployment, I don't see how anyone could conclude the accident was a result of an uncommanded TR deployment from the available evidence. But Boeing certainly concluded that must have been the most probable cause... "On Monday, 9 September 1991, the Boeing Commercial Airplane Group asked its customers to replace a valve in the thrust reverser systems that could cause the thrust reverser to deploy in flight." http://community.seattletimes.nwsource.com/archive/?date=19910909&slug=1304510

The investigation into Lauda Air Flight 004 determined that the probable cause was the deployment of the left engine thrust reverser (TR) during climb. An unsuspecting crew would not be able to recover control of the aircraft after such an event. Damage to the components involved in the crash prevented identifying a definite cause of the TR deployment.
TL;DR: The hydraulic system that opens and closes the TR includes two separate valves. The investigation found certain electrical and hydraulic failures that could result in both of these valves malfunctioning, resulting in uncommanded deployment of the TR. 767 aircraft with different engine models used a mechanical system to control the TR valves, which were not susceptible to those faults.

Information here summarized and quoted from the accident investigation report, you may refer to it for more detail.
Two important components involved in the investigation were the Hydraulic Isolation Valve (HIV), which determines whether hydraulic fluid can flow into the TR system, and the Directional Control Valve (DCV), which directs hydraulic pressure from the HIV to either deploy or stow the TR. In normal cruise flight, the HIV should be closed, and the DCV should be commanding the TR to be stowed, which provides redundant control of the hydraulic side of the system. The report analyzes electrical and hydraulic failures that could have resulted in both of these valves being in the wrong position, allowing uncommanded deployment of the TR.
Both valves are controlled electronically based on the position of the reverse thrust lever in the cockpit. The HIV normally will not open without the landing gear sensing the airplane is on the ground, but it is also controlled by an "auto-restow" system.

The auto-restow circuit design was intended to provide for restowing the thrust reversers after sensing the thrust reverser cowls out of agreement with the commanded position. The auto-restow circuit powers the HIV to open regardless of indications from the air/ground circuit.

If the aircraft senses that the HIV opens while in the air, a REV ISLN (reverser isolation) message is given to the crew. About 6 minutes after takeoff the crew started to discuss an intermittent appearance of this message, and after referencing their manuals determined that no further action was necessary. The TR opened about 9 minutes later.

That an electrical wiring anomaly could explain the illumination of the "REV ISLN" indication is supported by the known occurrence of wiring anomalies on other B 767 airplanes.

With the HIV open, hydraulic power would be available to the TR system, but the DCV should still command the TR to be stowed. The DCV was also electronically controlled.

The investigation of the accident disclosed that certain hot short conditions involving the electrical system could potentially command the DCV to move to the deploy position in conjunction with an auto restow command, for a maximum of one second which would cause the thrust reversers to move.
...
Boeing could not provide test data or analysis to determine the extent of thrust reverser movement in response to a momentary hot-short with a voltage greater than 8.2 Vdc or the ability of the thrust reverser to return to the stowed position after tripping of the circuit breaker associated with the source of the hot-short.

So the investigation determined that it was possible for electrical issues to cause the TR to deploy in flight, but they could not determine whether the electrical system on the accident plane had any issues.

The degree of destruction of the Lauda airplane negated efforts to identify an electrical system malfunction. No wiring or electrical system component malfunction was positively observed or identified as the cause of uncommanded thrust reverser deployment on the accident airplane.

Electrical issues were not the only reason the DCV could malfunction. Contamination in the hydraulic system could also cause the DCV to command TR deployment. But the investigation was not able to rule out contamination of the DCV in question.

The condition of the left engine DCV which was recovered approximately 9 months after the accident, indicated that it was partially disassembled and reassembled by persons not associated with the accident investigation.

Without knowing the original condition of the DCV and aircraft wiring, the investigators could not identify a definite cause. Some of the issues found in the investigation were addressed by airworthiness directives (AD's) from the FAA, and by design changes by Boeing and the equipment manufacturers. This consisted of making the wiring less susceptible to faults and the valves less susceptible to malfunction from contamination.
The electrical failures were dependent on the configuration of the aircraft electrical system, and the hydraulic failures were dependent on the design of the valves. The report includes an FAA letter analyzing whether a similar failure could occur on other Boeing aircraft.
The accident airplane was a 767 with PW4000 engines. Once the investigation identified the above issues, the TR's on these planes were deactivated until a fix could be implemented. 767 aircraft with JT9D or CF6-80A engines were excluded at the time from any corrective action:

Since these thrust reverser systems employ mechanically actuated directional control valves, it is felt that they do not possess the same potential for inflight reversal as those systems listed above.

757 aircraft with PW2000 engines were very similar in design to the 767/PW4000 system, so system checks and valve replacement were mandated.
747-400 aircraft had similar systems to the 767, but were not immediately affected, because aerodynamic differences meant that a TR deployment in flight would not be as serious. The same fixes were to be implemented though.
767 aircraft with CF6-80C2 and RB211-524 engines had a different system, but inspections and tests were anticipated until design changes were made or determined unnecessary.
757 aircraft with RB211-535 engines had a different hydraulic design that wasn't susceptible to contamination failure, but the electrical system was analyzed for potential issues.
737 aircraft with CFM56-3 engines were not found to have the same issues.


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Any script to plot multi axis FDR / flight-test data (such as the ones used in air crash investigation)?
I am looking for a script or tool to create flight test and/or FDR plots with several vertical axis, such as the ones used in aircraft accident investigations.
Does anyone have any hint on a MATLAB or Python script that does it? I have the data and I know how to code, just didn't want to reinvent the wheel here.
Example:

Source

Welcome to Aviation.SE. I'll wait for the opinion of the other members, but I am afraid your question might not be on topic here. You are not properly asking an aviation question here, but only how to make a specific plot in Matlab/Python/whatever

Hi Federico! I thought that someone that works in the aircraft industry (just like me) would have already created a script for such objective. I am afraid a Python or MATLAB programmer/enthusiast would hardly have access for flight data to play with.

I see your point, and that's why I did not immediately hammer your post down. The problem is that from a quality point of view, this question is little more than "please give me the code/solution" that is a bit frowned upon around stackechange. Should the others agree with you, no problem. If instead they should vote to close this question, stick around, gain a bit of reputation, and pass by chat!

Do you have raw data taken directly from say a QAR or test telemetry/recording device, or processed data that's already converted to engineering units and standard sign conventions? (an example of the latter is "climbing right turns are positive", which is what the NTSB uses for all their FDR plotting)

In fact I have both raw and engineering units data.

The problem with predefined scripts is that most of the time, the variable designation doesn’t match, anyway, so it’s almost as quick whipping it up from scratch... at least for the most common parameters.

I don't think these plots are generated from Matlab or Python, but from special-purpose software. This was discussed in chat a couple of months ago, and one example is Insight Analysis, which offers a GUI interface to put together the kind of chart you're looking for. It's definitely not the only such tool, though.


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Are there any aircraft where the wings are swept forward of the cockpit?
Are there any aircraft where the wings are swept forward to form a C shape ahead of the cockpit? Something like this:
  --  --
 //    \\
 || /\ ||
 || || ||
 \\_||_//
  \____/

I want to do a research on that kind of aircraft and there are many science fiction examples, but I wonder if there are any real-world ones? If so, what is that wing configuration called?

I'm voting to close this question as off-topic because it's about fictional space ships, not about aviation.

The experimental Grumman X-29 had forward swept wings, but they didn't actually go so far as to be forward of the cockpit.  (https://en.wikipedia.org/wiki/Grumman_X-29)

I have voted to reopen this question. The question seems to be answerable, and in fact, is answered satisfactorily, if in fact there are no real world aircraft with that wing configuration. The fact that the question is based in science fiction does not mean it's not about aviation. If the reason there have been no aircraft shaped like that, an answer that explained why it would be impractical may actually be more beneficial to the OP.

This wing planform would be statically unstable and needs to be much heavier than a straight or sweptback wing.

It is easy to find forward swept wings, but C shape seems to not be interresting enough to be experimented

The closest thing from the real world that comes close to the ones you found on deviantart are "Canard Aircraft"

If you read about this concept you will find that it is complicated to implement it succesful.
Then most of the art employ a forward swept wing, this has some complications as well. I would suggest you read some more about the NASA X-29

As far as I know a combination of the two has never been demonstrated in real life and only exist in fiction, therefore there is no general name for as far as my knowledge goes.

If you find a picture of the starship with flaps deployed, the canard is even slightly swept forward. Yes, the Starship was a subsonic variable-geometry aircraft.

I think the Hansa Jet from the 60's is the only production aircraft with forward swept wing. (There were some gliders that tried it too) The sweep creates more problems than it solves, however. https://en.wikipedia.org/wiki/Hamburger_Flugzeugbau_HFB_320_Hansa_Jet

The Junkers 287 was a WW2 testbed that had forward swept wings, although they didn't extend past the cockpit at the very front of the fuselage. If the 287 had a more conventional bomber cockpit location, the wings would have been swept to about the cockpit location.
This was a real hodgepodge of aircraft parts. The fuselage was a HE177, rear landing gear from a JU352 transport, and front landing gear came from crashed B24's.
The forward swept wings were said to give better response at lower speeds, as the early turbojets didn't accelerate very quickly.
It never went into full production.


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Could the autopilot have rectified the flight path without any crew input on the Aeroflot Flight 593?
In the case of the Aeroflot Flight 593 air crash, could the autopilot have rectified the flight path of the Airbus at any point if the crew had not attempted to correct the spin, even while partially disengaged as it was after the son applied to much force to the control column?

Despite the struggles of both pilots to save the aircraft, it was later concluded that if they had just let go of the control column, the autopilot would have automatically taken action to prevent stalling, thus avoiding the accident.

I've update your question for you. next time please use the [edit] function

The question was much better with the quote in it explaining some background instead of requiring everyone (except the air-crash junkies) to click the link to find out any information at all.

The PIC had given his seat and controls to his son (a visitor in the cockpit without any flight qualifications). The autopilot was in perfect control of the A310 until the son of the PIC had disengaged the automatic aileron control by applying sufficient control force. Up to a certain banking angle, fully engaging the AP would have resolved the problem. Without control over the ailerons, the AP could not recover the plane's attitude. The banking angle was out of the operating range, and the plane was not able to maintain its altitude.
Unfortunately, both pilots had trouble to become aware of the situation, and they also had a lack of understanding of the A310 controls. After fully disengaging the AP, the AP could not help with the lateral control any more.
This is very simplified, of course. A lot of elements contributed to this "accident". I recommend to read the Investigation report.

@bogle: Excellent, simple explanation of the situation! While not an exact corrollary, it backs up the generic Airbus advice that in an abnormal situation "Don't fight the aircraft, let it go"! AF447 being a similar case in point. Had the crew, and in particular the F/O let go of the side-stick, the aircraft would have righted itself, by itself. A very tragic situation.


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Is there any specific reason why Delta Air Lines doesn't have its own callsign?
Many airlines have their own callsigns for use over the radio. A British Airways plane is called "Speedbird", US Airways was "Cactus", etc. So why doesn't Delta Air Lines do the same? It would seem to need one a lot more than others, since "Delta" is the NATO Phonetic Alphabet name for "D", so it would seem to present a huge potential for confusion.
Atlanta airport, Delta's headquarters, uses "Dixie" for the letter, specifically to avoid confusion with the airline. It just seems easier and safer to me for the airline to adopt a callsign rather than deviating from the phonetic alphabet.

Same reason they allow Clarence Over and his co-pilot Roger to fly.

@BrianDrummond - but will they give Clarence clearance for Victor's vector?

@BobJarvis-ReinstateMonica Roger, Roger.

@HiddenWindshield: I been listenin' to that crap since I was at UCLA! You tell your old man to try dragging Walton or Lambier up and down the court all night!

Note that the original title question was Why doesn't Delta have its own callsign? so most answers address that question.

@HiddenWindshield I had to revert your edit. There are already answers to your original questions, and we cannot tolerate edits that make answers obsolete. If you have a follow up question, ask it separately.

@BrianDrummond To say nothing of Michael Mayday...

@Federico Ok, I've asked a follow-up.

The problem isn't with the callsign, the problem is with the name. They should've picked a better name.

Delta Air Lines uses the ICAO three-letter designator DAL and the ICAO telephony designator (also known as callsign) DELTA.
In general, callsigns should be similar or equal to the name of the airline according to the following ICAO rules:

3.2 In the registration of telephony designators the following rules will apply:
a) the chosen telephony designator should attempt to resemble the name of the aircraft operating agency or its function
  and be distinct and dissimilar from any other telephony designators in Doc 8585. Ideally it should reflect correlation
  between the three-letter designator, the telephony designator and the name of the aircraft operating agency or its
  function (examples: ARO – ARROW – Arrow Aviation; RAJ – RAJI – Raji Airlines);
b) in order to reduce the length of transmission the telephony designator should be brief, comprising if possible one
  word of two or three syllables. It should not exceed two words;
c) three-letter designators may not be used in phonetic form as telephony designators. However, telephony designators
  of long standing (such as KLM or TWA) may be retained, provided that an acceptable alphabetic representation is
  used (example: KAY-ELL-EMM); and
d) the telephony designator should be easily and phonetically pronounceable in at least one of the following languages:
  English, French, Russian, Spanish.

(ICAO Doc 8585 3. Telephony designators, emphasis mine)
Different callsigns can exist for two reasons:

Old callsigns: Several old airlines use callsigns that existed before these rules were made, like e.g. KLM as mentioned in c). British Airways inherited the callsign SPEEDBIRD from BOAC in 1974, which in turn inherited it from Imperial Airways in 1939. It is named after the design of the Speedbird logo.
Conflicting callsigns: When the airline name is too similar (or equal) to an existing callsign, a different one must be chosen, like e.g. Norwegian mentioned in J. Hougaard's answer. US Airways inherited CACTUS from America West in 2008:

Early in its history, the airline used the call sign “America West” but it often caused confusion with other airlines ending in “west” (Southwest, Northwest, Skywest). The FAA suggested that America West come up with a new call sign. The company held an employee contest to come up with the new name. Cactus was chosen.

(aerosavvy.com)

While Delta Air Lines is quite old ("Passenger operations began on June 17, 1929", Wikipedia), it did not chose a different callsign. I can only speculate on why, but note that the ICAO phonetic alphabet is only officially used for civilian aviation since 1 April 1952. Before than, other alphabets were common, including the Allied military phonetic spelling alphabets, which used DOG instead of DELTA, so there was no conflict at the time.
Using a different word when confusion is likely (like DIXIE in Atlanta), is explicitly allowed in the US:

ATC facilities may also request pilots to use
  phonetic letter equivalents when aircraft with similar
  sounding identifications are receiving communications on the same frequency.

(AIM 4−2−7. Phonetic Alphabet)

"The company held an employee contest to come up with the new name." ... the winner should have been Hairy McAirface.

+1 for the "Speedbird" history lesson alone!

@Cœur Thankfully, it wasn't an online competition. ;)

+1 for pointing out that the 'DELTA' callsign predates the ICAO phonetic alphabet. This is almost certainly why Delta was allowed to use that callsign. If someone tried to register, say, "JULIET" as a callsign today, it would most likely be rejected. Also, if the ICAO phonetic alphabet were being created today, they probably would've picked something other than 'Delta' for 'D.'

Delta DOES have its own callsign. It's "DELTA".
There are literally thousands of airlines in the world, many of which have designated radio telephony callsigns. Some of them are very close or even identical to the airline name, others are more diverse.
Bianfable gives a good explanation regarding the origin of the Speedbird callsign. While not the case with Speedbird, there are examples of airlines who needed to choose callsigns very different from their name simply because the other callsign was already in use by someone else. One example is Norwegian. They use the callsign "Nor Shuttle" (and a few others), probably because the callsign "Norwegian" was already in use - by the Norwegian Air Force. But, generally speaking, a callsign will be close or identical to the airline name.
A full list of airline callsigns is available in ICAO DOC 8585.

The downvoter is very welcome to leave constructive criticism so that I can improve my answer

Your speculation about "Speedbird" is wrong.  The Speedbird logo and callsign pre-date BIH by about 70 years.

@Mark Thanks for the tip. For another times sake, feel free to edit an answer if it contains information that is obviously wrong.

Ok, perhaps I should have worded my question differently. Why doesn't Delta Airlines have a callsign that's different from a NATO alphabet word?

@StephenS At the time this answer was posted, it did address my question as I had worded it.

If we look away from airlines for a minute, almost all callsigns are simply letters (and numbers) from the phonetic alphabet.
Because Radio Telephony uses fairly specific formats, the likelihood of confusion is pretty low. " Delta 1234, after the landing traffic, line up and wait" simply can't mean anything other than what it's supposed to. It's got no other interpretation that makes sense, and isn't really any different to "November 123 Foxtrot, after the landing....."
Remember, the phonetic alphabet is there to make letters easier to understand - it's not there to denote that you are speaking in letters. There are lots of words in the alphabet that are just normal words (and deliberately so).

That is true. However, you can a Delta flight number 8074 and you can have a aircraft registered as D-8074 on the frequency. It is always a callsign, but delta can be just a letter in the callsign, not the airline callsign.

@ymb1 I have only the Czech phraseology L-document and such a prefix is only possible, not necessary. Also, I don't recall hearing it in my listenings but I don't do it too often. "Type   a)–the   characters   corresponding   to   the registration marking of the aircraft, or Type  b)–... aircraft operating  agency  followed  ...the registration marking...; Type  c)... operating agency, followed by the flight identification. Note 1:The   name   of   the   aircraft   manufacturer or of the aircraft model may be used as radiotelephony prefix to the Type a) callsign."

So the "important step" is actually only a possibility in a note. I am pretty sure the document cited follows the ICAO and EUROCONTROL rules.

@VladimirF Callsign clashes are always a problem and a concern, especially when callsigns are shortened (Common in the UK, at least) or very similar. That's really something for each individual controller to notice and handle.

@Dan I know. The answer could be read as suggesting it cannot happen, though.

@VladimirF At least there will still be one difference between German-registered callsigns and Delta ones in Europe: The Delta callsigns will almost certainly end in "Heavy."

In addition to the other answers I found a paragraph on HistoricWings.com which mentions this "problem".

Local Variations Based on Need
The international standard remains not quite completely standard, however, even to this day.  You might notice, for instance, that when flying from Hartsfield-Jackson Atlanta International Airport, where Delta Airlines is based, the air traffic controllers and ground controllers might use “Dixie” or “David” instead of “Delta” so as to avoid confusion in routine communications with the name of the main airline that is hubbed there.  An example might be help to demonstrate why this important:

Delta 551, Atlanta Ground, confirm Delta; taxi via Lima, Delta, Mike to runway 27 right.

Clearly, this is a lot more understandable if the phonetic “Delta” is swapped out for “David”, as follows:

Delta 551, Atlanta Ground, confirm David; taxi via Lima, David, Mike to runway 27 right.

It may have been different in the past, but the currently-suggested phraseology if a pilot doesn't report the proper ATIS code is "Verify you have information [letter]." Hard to confuse that instruction for anything else, even if the letter is used for another purpose elsewhere in the transmission. It's not strict phraseology though, just an example.

authors: Bob Jarvis - Слава Україні

authors: Vladimir F Героям слава


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What is the effect of aft centre of pressure movement on static longitudonal stability?
During studying for my Air Transport Pilot License (ATPL) I encountered a question answer which said that aft center of pressure movement increases longitudinal stability. If this is true, I cannot seem to wrap my head around the concept of why this is so.

yes, thanks for pointing that out, fixed in original Q

Welcome to Aviation.SE!

Moving the CP aft will have the same effect as moving the CG forward: increased longitudinal stability.
The arm of the Lift force is now increased and the ratio of momentum generated by the wing vs horizontal stabilizer is decreased, leading to positive longitudinal stability.


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What is the theoretical maximum velocity of electric aircraft?
I'm wondering about theoretical maximum velocities of supersonic electric aircraft. I think the fastest demonstration of any type of aircraft has been close to mach 10. This was done using a rocket engine, so propulsion was not limited by air characteristics as much as an electric motor + compressor's propulsion would be (I think).
Under best conditions; Assuming an incredibly high power to weight ratio of motors, extremely aerodynamic design, strongest materials, etc.
Theoretically, does anyone know what the limiting factors in the velocity of an electric compressor propelled supersonic aircraft would be (barring energy use)? Does it depend on size, etc?
Could it reach mach 2+?
Thanks a lot in advance for any input.

Just to clarify, you're limiting this specifically to electric motors driving a compressor and not some (for example) yet-to-be-invented scramjet-like electric engine, right?

Well yeah, electric motors to compressor is what I mainly want to know about since it theoretically exists and probably has defined limitations. Though the latter would be increasing the domain from what current technology can do to what is possible given the laws of physics, regardless of current technology. That would be awesome to know about too.

Since you seem not to be concerned about the usability of this hypothetical electric aircraft, let's make some simplifications:

The aerodynamics are so good that it does not create any drag. This is completely unrealistic but helps a lot to simplify things.
Structure, controls and propulsion are so advanced that they leave one third of the take-off mass for batteries. Who needs payload anyway?
Efficiency is 80%. Not even electric propulsion can be lossless.
Energy storage is the best current technology has to offer. This would be about 1.8 MJ per kg of battery for non-rechargeable lithium cells.

To accelerate a battery of the mass m to a speed v needs an amount of energy $$E_\text{kin} = \frac{m}{2}\cdot v^2$$
Flying Mach 2 at sea level is impractical; it helps to climb to at least 6.000 m (20.000 ft) to do so. This adds potential energy: $$E_\text{pot} = m\cdot g\cdot h$$
Conveniently, the result is independent of mass, so the potential maximum speed is $$v_\text{max} = \sqrt{2\cdot\frac{1}{3}\cdot0.8\cdot1{,}800{,}000\ \mathrm{m^2\ s^{-2}} - g\cdot h}$$
If we solve this for 6000 m, the speed at the end of the acceleration is 949.3 m/s, which is already Mach 2.966. If you prefer to use rechargeable batteries (1 MJ/kg), the maximum speed drops to Mach 2.15.
If you start to add a reasonable figure for drag, you won't even make it to the speed of sound before the batteries are empty. Currently, propellers are the most sensible way to convert electric energy into thrust, and large, low-speed propellers are the most efficient type. If you think to drive a conventional compressor with an electric motor, its subsonic efficiency is already far worse than the assumed 80%. Even its mass is not yet competitive with conventional gas turbines.

@ymb1 Thank you for telling me. No apologies needed.

The density of energy storage is also tempered with the rate at which it can be extracted from the material. Therefore the power available to the supply will have temporal capacity limits, however that of course doesn't prevent the possibility of entirely depleting the primary cells over many hours into the supply and then being consumed in seconds by the engines.

@jCisco: Absolutely right, I did not cover any of the constraints. A more complete answer should include this, but I felt that just looking at how much energy it needs to accelerate would show how far away supersonic electric aircraft are.

Rather than write a contrary minority answer, how does your answer extend to electrohydrodynamic thrust.  (Ionic Wind).  I don't have the link but Steven Barrett of MIT had a paper on this you might find very relevant.

@jCisco: I used 80% conversion efficiency. Even if electrohydrodynamic thrust is more efficient (which I doubt), the result would not look that much different.

That is exactly the point of the research i mentioned, which gave results of 100+ N/kW vs a jet engine which is ~2N/kW.   You can get HTML on the first link and the second is the full pdf . http://rspa.royalsocietypublishing.org/content/469/2154/20120623.short
http://rspa.royalsocietypublishing.org/content/469/2154/20120623.full.pdf

@jCisco: Thanks for digging this up!

I agree with the sentiment on the difficulty of electric airplanes, but it's worth pointing out that there are now electric airplanes with ~60% cell mass fraction at MTOW: https://en.wikipedia.org/wiki/Eviation_Alice#Design

@Gus: So far this is all hot air. As in: The prototype burned and was destroyed. To say that there are now electric airplanes with ~60% cell mass fraction is simply not true.


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Does it make sense to do an emergency landing without nose gear in order to reduce stopping distance?
Would a pilot decide to land without the nose gear down to increase friction if for example all the engines have suffered a flame-out and there is only a very short runway available ?

You usually can't select the nose gear to be up with the main gear down.

@RonBeyer  You can manually extend whichever gear you wish, without extending the others. Probably a bad idea, but certainly possible.

@RalphJ I'd say that's the exception rather than the rule, i know many aircraft where the emergency release or extension system is a single handle or hand pump

One of the (several) reasons this wouldn't normally be a good idea is that it kills a lot of your directional control on the ground. Also, if you're planning ahead to land in a place that is so short that you're so concerned about runway overrun that you're considering intentionally crashing the plane, a better plan is usually to land somewhere else instead. :)

@RalphJ you can, can you? What aircraft are you talking about, pray tell?

I can't think of a GA aircraft which allows selectable gear dropping.  The normal mode is all or none.

@egid B-737, all variants.

If you're going to land on a paved runway, nose gear would help you control the plane. If you're going to land off-runway, decreased friction - not increased - from landing without nose gear is likely to be a gentler crash and do less damage to the plane and passengers.

If landing with the nose gear would be good, wouldn't a full gear-up landing be even better?

To my knowledge, no established procedures exist for any contemporary civilian airliner that would land with any gear up to decrease landing distance.
However, contrary to other answers/comments, in some aircraft (among others, the B737 NG, check out http://www.b737.org.uk/landinggear.htm for a picture of the manual extension panel) it is POSSIBLE to deliberately lower only selected gear by using the manual/alternate extension system, which usually includes manually releasing the gear uplocks to let the gear free fall to its downlock position. By releasing only the desired downlocks, partial extension can be accomplished.

I added a reference to the B737NG as a minimum example. This probably applies to several other aircraft as well, however, I am not as intimately familiar with their hydraulic systems to comment on any other particular models.

The answer to this question is best determined in light of risk evaluation.  Undoubtedly, metal on asphalt has a higher coefficient of friction than a nosewheel.  However, there will likely be some level of repair. It is however, not uncommon for nosegearless (is there such a word?) landings to result in amazingly little damage to the aircraft.
Here's the rub (no pun intended): A metal skid offers less control certainty than a spinning nose wheel. Yes, differential braking on the mains can provide steering, but a skid plate is just not the same as a rolling nose wheel. So not only is the behavior, and noise different for the pilot, but the aircraft attitude will be pitch down. The unfamiliar visual presentation, the unfamiliar noise, the unfamiliar handling characteristics, and the lack of experience conducting similar operations create a higher workload for the pilot, and reduce his ability to rely on common cues.  So I would avoid changing things unless there was an extremely compelling reason to do so.
Forget talking about braking on most gliders.
With the nose wheel steering, one can sashay the plane side to side, especially for a light aircraft landing on a wide runway.  That increased maneuvering can help bleed of additional speed.  Think of it as a way to extend your landing roll.
Also, if the nose wheel has steering command (not a free caster), then the nose wheel will consume some energy during the sashay maneuver, as it will present a side load resistance (friction).
While the nose wheel is less likely to heat up like the mains, and there are seldom fuel tanks near the front of the aircraft, there are fuel lines, and they frequently run near the bottom of the fuselage.  So keeping them off the ground can reduce fire risk.
I always do a "brake check" checking the firmness of the brakes prior to landing.  Once, a C-208 failed that check with a bottoming pedal on the left side.  I landed at a 3500 ft strip, and was able to use beta to slow the aircraft down, and used beta and the right brake to get to the ramp.  Of course a C-208 does not have a retractable nose gear, but it was nice having the directional control of the hose gear during the landing and taxi phase. If 3500 ft appeared to be inadequate, my option was to go to a longer field, and face the scrutiny of everyone there, including the FAA.
One additional thought, I had a checkout in a level D simulator where they simulated tire failures.  I don't know if they could simulate failure of a gear extension.
A more specific answer is possible if you were to define the intended aircraft.

Near as I know, the answer is no, you cannot nor would you want to.  The friction from grinding the nose section of the aircraft may indeed slow the aircraft quickly but sparks and debris kicked up during the landing could create a FOD and fire hazard.  It would probably be best to land w/ all three gear down and locked and execute a revision short field approach using thrust reversing and braking throughout the ground roll.


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Is there a relation between the Mode 3/A Code and the ICAO aircraft address?
I would like to know is there is any way to match mode 3/a code (which is assigned by ATC to aircraft) and ICAO address of the aircraft. I mean how mode 3/a code is assigned to each aircraft by ATC? Is that unique for that day or certain time period? Is it possible that same address is assigned to more than one aircraft? Is there any relation with aircraft's own 24 bit ICAO address?

Welcome to aviation.SE! Have you looked through our existing transponder questions? It looks like this one is quite similar to your question?

There is no relation between the ICAO 24 bit aircraft address and the 12 bit Mode A code. The 24 bit address is unique to the aircraft and stays with the aircraft as long as the aircraft has the same registration. The Mode A code changes from flight to flight and often during flight.
The Mode A code is assigned by ATC based on a local or regional assignment scheme. There are Mode A codes that can be used by many aircraft in one area simultaneously, such as VFR codes (1200, 7000) for flights that are not under air traffic control. For IFR flights, the Mode A code is unique for the control area at that given time. When aircraft move from control area to control area, a code conflict can occur when two aircraft with the same code end up in the same area. In such a case one aircraft will be given a new code.
There are various schemes to prevent code conflicts from happening too frequently. See this answer for more info.
Quite recently (in the last couple of years) IFR flights in Europe can operate under conspicuity code 1000 which is a signal to the flight data processing system to use the Mod S downlinked aircraft ID for identification and flightplan association. This allows many aircraft flying in Mode S surveillance airspace to use code 1000 simultaneously, freeing up Mode A codes and reducing the number of code conflict.

"he 24 bit address is unique to the aircraft and stays with the aircraft as long as the aircraft has the same registration." --> The 24bit address is unique to the transponder AFAIK, and not to the aircraft. If you switch transponders, you will have a different 24bit code.

@SentryRaven if you switch transponders, you have to recode the new transponder such that it has the right 24 bit address of the aircraft  it is installed on. You are not allowed to fly with the 24 bit address of another aircraft.

Isn't this only true for transponders that have add-on encoders? If I am not completely mistaken, some transponders have a hardcoded 24 bit address. But I am only 70% sure on that...

No, it is a requirement on the transponder that the 24 bit address is configurable. The address belongs to the aircraft registration, not with the transponder.


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Where can I find (online) manuals for refueling A320/B737 for a given destination?
Surely, airline crews must have manuals/apps by which they calculate the (minimum) amount of refueling before departure to a given destination. I have been looking online for such sources, with zero hits.
Specifically, I'm intersted in such free manuals/apps for the Airbus A318...A321 and Boeing B737 families.

I suspect that you will only find them for flight simulation since there is no need for real world manuals to be online. Also related

Fuel calculation is part of flight planning, using the information usually provided by the manufacturer to the customer in the FCOM (I believe it's under a non-disclosure agreement albeit some appear from time to time on sites like Scribd!) Simmers use tools like Advanced Flight Simulation Fuel Planning.

Very rarely will a manual directly be used by flight crew for calculation of fuel uplift.
Flight crews generally receive an Operational Flight Plan prepared by the operator (the airline), or an agent of the operator, where calculations have been made for how much fuel will be required for the specific flight, and necessary reserves. Flight crew may elect to revise the fuel required to provide additional margin for weather, traffic or other factors.
The calculations made for the Operational Flight Plan are made with flight planning software, which in its turn uses data from performance manuals/data sets, and takes a large amount of parameters into account (routing (duh!), wind, flight altitude, speed, aircraft weight, load distribution (c.g.), alternate airport availability etc).
Flight crew can however make simplified fuel calculations using the FPPM for the aircraft type (Flight Performance and Planning Manual) (Boeing). The flight profile is however generally quite limited to a few climb/cruise/descent schedules, and the data is not what would be used on a normal line day. Distribution of FPPM (and other manuals) is generally restricted. If you however would come across a replica of a FPPM, you could probably make a usable fuel calculation using the instructions within it.

I believe the FMS also calculates fuel estimate when the flight plan is programmed. It is still less precise than the one provided by dispatcher, because FMS does not have the detailed wind forecast the dispatch system used.


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What is the difference between EPR and rotor speed as thrust setting parameter?
Amongst various thrust setting parameters, Engine Pressure Ratio (EPR) and fan rotor speed are two of them. Does anybody know why GE uses fan rotor speed and P&W uses EPR as thrust setting parameter?

While the true 'reason' is probably buried in some engineering notebooks from 60 years ago, it basically boils down to a design decision by the team designing the engine controls.  Both methods work, and both companies have a list of reasons why they think their solution is 'best'.
P&W will tell you that EPR is a better indication of engine thrust, and they're right.  But it relies on pitot probes to measure the pressures within the engine.  Flow stability means response can be slow or erratic and the probes can be clogged causing problems. OTOH, it can indicate problems (unrelated to the probes) due to engine damage.
GE prefers to use N1.  This is a simple speed indication of the fan.  It's not a direct indication of thrust but is directly correlated.  The big advantage is that it is extremely reliable and stable.
A good explanation is available from the Flying Engineer.


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What does a white over red VASI indicate?
I have found the following mnemonic's to remember Visual Approach Slope Indicator combinations:

White over White, you're high as a kite. / you'll fly all night
Red over White, you're alright.
Red over Red, you're dead.
White over Red, unsaid / you're under head

What does White over Red exactly mean? Does you're under head mean your low? I can't seem to find it anywhere.
Mnemonic Src: https://en.wikipedia.org/wiki/Visual_approach_slope_indicator

It remembers you to stop flying upside down before landing.

"White over red" isn't actually possible unless the VASI installation is badly off, or else if you're upside down on final.  If the top lights are white, you're above their glidepath angle, and if the bottom lights are red, you're below theirs.  With a standard VASI installation done correctly, you can't be in both places at once -- if you're above the path for the upper lights, you're above the path for the lower lights as well, and vice versa.
The "white over red" is simply a nonsense answer thrown in to some test questions in order to see who understands what's going on with a VASI system.  Most folks will remember that when you're on the proper glidepath you'll have one set of red lights & one set of white lights, but which one should be where?  As long as you understand how the lights work, you can correctly answer that red above white = on glidepath.
My best guess at the mnemonic is that they're suggesting you're "standing on your head," or in other words upside down, in order to see the lights in that position.  I wouldn't get too wound up about the lame rhyme in the memory aid.  Just know that with all white, you're high; with all red, you're low, and with red over white, you're on path.

I feel like I heard it as "you'll land on your head". That being the "this is impossible unless you're inverted" explanation you mentioned.

The lights will look the same when flying inverted. Their colors depend on eye position only, and being inverted won't change that.

@PeterKämpf  The idea is only that the "over" apparent relationship flips, to where the lower, red, VASI is "over" the upper, white, one, since the observer's frame of reference is now inverted.  The red one is still red & the white one is still white, of course.  It's a far-fetched "unless..." exception to the general statement that "you can't see white over red...", nothing more.

@RalphJ: Then climbing while inverted becomes a CFIT hazard. It's better to stick to fixed directions for up and down, regardless of attitude.

@PeterKämpf  I'm good with fixed directions, but "frame of reference" explains what the originator of the mnemonic had in mind.

Thanks Ralph! I updated the Wikipedia page where I got the Mnemonic to clarify this.

The VASI has two sets of lights that appear white or red based on the angle from which it is viewed. If the top light is white, it means that the aircraft if flying too high. If the bottom one is red, it means that the aircraft is flying too low.
If we go by this, a white over red cannot happen as you cannot be too high and too low at the same time.
It would be better to remember only the first three lines, as given in the answers to this question and be done with that.


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Do visual docking systems improve safety?
Are there any studies that shows A-VDGS (Advanced Visual Docking Guidance System) is improving the safety of aircraft movements on airports?

What is an A-VDGS?

@Terry Those are some kind of monitoring system helping to dock the aircraft to the passenger boarding bridges.

At the date of writing, assuming you mean scientific-published studies and restricting to AVDGS, I would say no, I can't find any study related to safety of AVDGS:

https://scholar.google.com/scholar?q=%22Advanced+Visual+Docking+Guidance+System%22 (all of these articles do not look into safety)


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In the Philippines' Civil Aviation Regulation Part 7, what does this part mean?
In the Philippines' Civil Aviation Regulation Part 7 it says

individual certificate of airworthiness of the first production aircraft under the type certificate

I want to know what does "first production aircraft under the type certificate" means.

"first production aircraft" indicates the first aircraft built as part of the "production" run (as opposed to the ones built for the test phase, that are not part of the "production").
"under the type certificate" indicates that the type of aircraft has achieved certification and can be legally flown in the Philippines.
All together it identifies the first production built aircraft of a certain type after the certification was provided (in this case for the Philippines).


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How was a looping possible with an Alaska Airlines plane?
Someone has stolen an empty airplane from Seattle Airport and crashed it down after performing some loopings. I am wondering how this was possible.
(Source)

where does in that article say that the aircraft performed "loopings"?

Are you asking how the loops were done or the aircraft was stolen? The title suggests the former but I feel you actually want to know the latter.

Most aircraft are capable of basic positve G aerobatics, provided you have a skilled pilot in the cockpit who knows what they’re doing.   Similar maneuvers have been performed by test pilots during demonstrations of large aircraft.  In all instances where it has been done, it has not been sanctioned by the company.  An unloaded commercial aircraft like that is going to have a pretty good thrust to weight ratio, which is going to help for doing vertical maneuvers like loops.
While precision aerobatics require a good deal of airmanship, the basics are pretty simple.  I’m not surprised that a mechanic, albeit a suicidal one, with no pilot experience was able to do a basic loop - and a terrible one at that.


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Can a plane turn around like on this photo?
I've never seen a plane do such a maneuver, have you?
Is this photo just a hoax?

Probably not real - that would need a pretty steep bank angle, so the contrails in the turn would appear closer together, or merge even.

@CrossRoads Agreed, the only way that can be done is if the plane is not leveled at all before and after the turn and keeping the exactly bank. in addition it must be slow and at high altitude meaning it's already loosing altitude

hoax, totally. that plane is travelling at about 550MPH and the forces required to turn it 180 degrees with a radius of ~two wingspans would destroy the plane and kill everybody in it.

We cannot know how much fast it's going, from that perspective we cannot tell it's going "slow" and even stalling due to it. But i agreed it looks like fake because the contrails in the turn looks too much parallel

@jean From the contrails we know a minimum flight altitude. From the wing loading we know the minimum airspeed at that altitude. It's a bit less than 550 mph, but the possible turn radius is still kilometers wide.

@PeterKämpf Yeah, unless it's falling like a brick and from that perspective we cannot tell =)

@jean even then the contrails would look very different - not a semicircle but a very long half ellipse.